The present invention relates to a method for the control of electromagnetic actuators for the actuation of intake and exhaust valves in internal combustion
As is known, drive units are currently being tested in which the actuation of the intake and exhaust valves is managed by using actuators of electromagnetic type that replace purely mechanical distribution systems (camshafts). While conventional distribution systems make it necessary to define a valve lift profile that represents an acceptable compromise between all the possible operating conditions of the engine, the use of an electromagnetically controlled distribution system makes it possible to vary the phasing as a function of the engine point in order to obtain an optimum performance in any operating condition.
A number of control systems enabling the valves to be moved by means of electromagnetic actuators according to desired timings have thus been developed.
These control systems have, however, some drawbacks. They are based on open loop control systems and require, when each valve is opened or closed, the actuators to be supplied with corresponding currents and/or voltages of a value such as to ensure that the valve, irrespective of the resistance opposing it, reaches the desired position within a predetermined time interval.
In this way, however, the valve is subject to an impact each time that it comes into contact with fixed members in the position of maximum opening (lower contact) or in the closed position (upper contact). This is particularly critical, since the valves are subject to an extremely high number of opening and closing cycles and therefore wear very rapidly.
Moreover, drive units that use these known control system are undesirably noisy, in particular at low speeds, precisely because of the impacts that take place during the phases of movement of the valves.
The object of the present invention is to provide a method for the control of electromagnetic actuators that is free from the above-described drawbacks and, in particular makes it possible to guide the movement of the valves during the contact phases corresponding to the open and closed positions.
The present invention therefore relates to a method for the control of electromagnetic actuators for the actuation of intake and exhaust valves in internal combustion engines, in which an actuator, connected to a control unit, is coupled to a respective valve and comprises a moving member actuated magnetically to control the movement of they valve between a closed position and a position of maximum opening and an elastic member adapted to maintain the valve in a rest position, which method is characterised in that it comprises the stages of:
a) detecting an actual position and an actual velocity V of the valve;
b) determining a reference position ZR and a reference velocity VR of this valve;
c) minimising differences between this reference position ZR and the actual position Z and between the reference velocity VR and the actual velocity V of the valve, by means of a feedback control action.